Abstract: According to the application of an 1 000 meters drilling rig in the underground mine, frequent phenomenon of in borehole accidents occurred in the overl ong (over 600 m) borehole gas drainage operation, certain causes of the borehole outburst, borehole collapsed, borehole jammed and drilling bit jammed were studied and the related treatment methods were provided.The paper held that the in borehole accidents occurred in the overlong borehole mainly caused by the seam geologica | structure conditions, the performances of the 1 000 meters drilling equipment and related facilities and the gas drainage technique with the overlong borehole .With the adjustment of the drilling technique and parameters, drilling tools improvement and the application of the special device, the borehole complement quality of the overlon g borehole could be effectively improved, and in borehole accident occurred posibility during the overlong borehole construction would be highly reduced.